Complementary metal-oxide-semiconductor field effect transistors (CMOS transistors) are often utilized in low power applications, such as low leakage electronic devices that require minimal electrical power consumption. One important application for CMOS transistors is in battery operated low leakage electronic devices, wherein battery lifetime is essential.
Leakage power refers to the rate at which electrical energy is consumed by an electronic device that is on, but not performing useful work. Leakage power arises from leakage current that is inherent in CMOS transistors. Specifically, in the context of CMOS transistors, leakage current refers to current that flows through a CMOS transistor when the CMOS transistor is off but the electronic device utilizing the CMOS transistor is on, which can result in electrical energy being dissipated even though the electronic device is not performing useful work. As CMOS transistors become smaller the length of the transistor channel region under the gates becomes shorter, which can result in increased leakage current and electrical energy dissipation. Generally, leakage current is undesirable, because electrical energy (e.g., battery power) is dissipated by an electronic device without the device performing useful work. Maintaining minimal leakage current has become increasingly difficult to accomplish as the size of CMOS transistors become smaller.